How to plan an efficient maintenance regime

WORLDWIDE: With the wind sector facing ambitious financial and energy targets, a robust operations and maintenance (O&M) strategy that considers the whole life of the wind turbine -- including life extension and repowering plans -- is essential.

Replacement… Making sure spare parts are easily available should be part of any good O&M strategy (pic: AWES)

When it comes to maintaining profitability over the lifecycle of a wind farm, even a 1% improvement in O&M can make a huge difference, especially when some turbines provide thousands of kilowatt hours of power a day. Downtime means a loss of income for a wind-farm operator, and any measures that can be implemented to avoid this will quickly pay dividends.

There is no doubt that putting together a structured, effective O&M strategy requires a lot of work, such as purchasing sufficient spares to maintain the sites and investing in training new technicians. But it means that services can be structured in a way that delivers the best performance and highest generation from the site.

Most electromechanical components will fail at some point without frequent maintenance, and this is especially true for wind turbines. Failure can be devastatingly expensive in terms of lost output, time and revenue. Having a comprehensive strategy in place before failures occur is critical, and this can be achieved by ensuring that O&M strategy development keeps pace with the wind power sector itself.

Below are the most important points to consider when preparing an O&M strategy.

1. Availability targets and site prioritisation

Many of the older O&M strategies are still driven by availability targets — the amount of time a turbine is operational — so this remains a major influence in work planning. Newer plans contain incentive payments for high generation. Penalty payments, introduced across Europe over the past four years, are in place if targets are not met and this remains the way in which the performance of an O&M strategy is measured.

It may also be applied in some areas where technicians are shared between sites, where site prioritisation becomes a factor in achieving availability targets. All prioritisation will result in a higher availability figure, which ultimately increases profitability and reduces the cost of O&M as resources are used more efficiently to meet the portfolio's needs.

2. Health and safety requirements

These can have a real impact on the planning of servicing and maintenance. No work may take place on a wind turbine without the correct documentation being approved. Complications in providing this documentation, or if it is of poor quality, can cause delays to major component replacement works, particularly if unusual work is required or new procedures are involved.

While it is true that there is more health and safety legislation to be aware of than ever before, it is a bad idea to try to bypass the preparation time. Rules are there for a reason, and cutting corners in an attempt to increase efficiency can often have the opposite effect, putting not only the daily operations at risk, but also lives.

3. Pre-emptive maintenance

Knowledge of a machine's particular quirks and faults is extremely helpful when planning maintenance. The early identification of any maintenance work required gives the freedom to choose the most convenient — and commercially advantageous — time to do work. When older machines are used, the history of the model, serial faults and common weaknesses are well known. With newer models, this kind of analysis will need more time.

Operators with a younger portfolio and lower failure rates often consider the creation of a pre-emptive strategy unnecessary and do not allocate time for identifying potential weaknesses. This can mean that if any downtime is needed, it is often much more costly.

4. Strategic service timings

Servicing of wind turbines has traditionally focused on time-based availability, with any maintenance executed as quickly as possible, irrespective of the cost, in order to avoid the turbine being out of circulation for long periods. However, this approach does not consider how much energy is currently being generated, and whether it is worth executing maintenance work at what could be an inconvenient time, for instance during a weekend. It makes more economic sense to shut a turbine down in a low wind period, when it is contributing very little power.

The same theory works in the adverse situation. A planned outage should not go ahead in the face of high winds. Not only can this result in a significant loss of generation, it can also put technicians and their equipment at risk. Use wind speed forecasts to estimate when downtime would be most effective. Call-off contracts, which commit to a minimum use of service over a period of time rather than set dates, can aid in speedy sourcing of services such as cranes, civil works, and turbine labour. Having quick-reaction plans can avoid any uncertainty by employees on what the best course of action is in the particular circumstance.

5. Organised collection of information

Ensuring that data regarding the turbines, frequent failures and common weaknesses is collected in an organised and accessible manner will make it easier to work out O&M costs and downtimes.

Although most operators diligently collect information and figures related to their wind farms, turbines and outputs, these are often stored in separate files. This makes accessing the maximum amount of data much harder. As a result, some operators lack a full understanding of their wind farm and struggle to develop O&M strategies that reduce operational costs and ultimately increase revenues. To gain as much information as possible on the current conditions of the turbines, regular inspections need to take place, not just by the service provider, but also the owner. This will allow them to gain an independent insight into the machine's current status. Recording all findings is also important to ensure that information is retained in the event of personnel changes.

6. Resource availability

Due to the young age and sudden expansion of the wind-power sector, many technicians are relatively new to the industry. This can result in work being restricted by the availability of suitably experienced people, which affects work planning. Therefore, a great deal of effort must be dedicated to ensuring that new technicians gain the experience and knowledge they need to become authorised technicians (ATs) at their sites. Technical training should be well structured from the outset, with awareness of wind-turbine safety rules underpinning all training.

The technology involved in the turbines will determine the time needed to gain the different levels of authorisation. It should be noted that technicians should not be rushed through training to gain authorisation, as this could have severe consequences.

7. Spares availability and parts pooling

As the industry gains more experience and collects more information on failure rates and the condition of the turbines, spares management will become more efficient. However, issues with spares provision has been cited as a reason for prolonged downtime across a number of wind farms in recent years. This reflects a widespread problem in the industry. Since the market is relatively small and lead times are long, there have been instances where spares availability has dictated what work can be done.

One of the key tasks for wind-farm operators is to build up sufficient spares reserves and identify key suppliers in the marketplace. However, the responsibility for this does not have to rest on one organisation. Parts-pooling programmes can help ensure that contingency stocks are kept high. The location, storage, and transportation of spare parts is crucial. Parts are frequently stored in warehouses close to the wind farm without adequate protection from the elements and are often in poor condition. In many cases the parts are unusable and need to be refurbished or repaired before they can be fitted. This can be avoided by storing parts in a central location under strictly controlled conditions.

A good relationship with the manufacturer can lead to a smooth spare parts provision. Partnering with other wind farm owners in the vicinity that run the same turbines can also help create a pool of parts you can access quickly.

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